Conventionally, hydrocarbon fluorides (HFCs) containing fluorine and hydrogen atoms have been used as refrigerants of air conditioners, car air conditioners and others. In addition, polar refrigeration oils such as polyalkylene glycol (PAG)s, polyol ester (POE)s and polyvinylether (PVE)s have been used in refrigeration cycles employing these HFCs as refrigerants, from the viewpoint of compatibility with the refrigerants. In such a refrigeration cycle, fluorine ions are often generated from the materials such as fluorine resins used therein. It is known that the ester-based refrigeration oil is then decomposed by the fluorine ions extracted into the refrigeration oil, resulting in corrosion of the metal sliding materials by the acid components and deterioration of the motor insulation paper. Thus in Patent Document 1, the amount of fluorine ions extracted from the fluorine resins was limited to a concentration of 1 ppm or less in the refrigeration oil, for example by previous heat treatment of the resins.